Conduit or duct for electric cables



Jan. 7, 1930. P. v. HUNTER 1,742,353

CONDUII 0R DUCT FOR ELECTRIC CABLES Filed July 21, 1928 2 Sheets-Sheet 1 d/iaylum iyl lzwwma Jan. 7, 1930. P. v. HUNTER 1,742,353

CONDUIT OR DUCT FOR ELECTRIC CABLES Filed July 21, 1928 2 Sheets-Sheet 2 I Patented a... 7,1930 I s I I i 1,74Z,353

UNITED "STATES PAT ENT OFFICE 1 I PHILIP vassim i uiirnn, or nomioiw, ENGLAND I CONDUIT on poor non nnncrnic CABLES Application filed July 21, ms, Serial No. 294,561, and in Great Britain au ust 12, 19271 This invention relates to conduits or ducts conduit with saddles all according to this for electric power cablesand has for its obinvention, and ject to furnish a conduit in which provision Figures 2, 4, 6, 8 and are cross-sections is made for expansion of the cable under load. of these conduits on lines in the various fig To this end the conduit or duct is proures numbered to correspond with the cross- 1 vided with saddles or raised'poitions at insectional views.

tervals in its length on which saddles the In Figures 1 and 2 the saddle A is moulded cable rests. The intervals between these or otherwise formed integral with the conduit saddles-and their height above the floor or A near its flanged 'or socket end where it re- 10 internal bottom surface of the duct will deceives the plain or spigot end of the adjacent 6O pend upon the nature of the cable, for inlength of conduit. The conduit in this ex-' stance upon its tendency to sag when unloadample is circular in cross-section and is ined by reason merely of its own weight. tended for use with a single cable B which The saddles are so roportioned and spaced is drawn in. j

15 that normally the ca leis supported by them Figures 3 and 4 illustratea conduit where clear of the floor of the duct by an amount the saddle A is formed at the spigot end of preferably just sufiicient to allow the cable the conduit and by way of example these figto rest upon the floor of the duct when it sags ures also show the conduit and saddle adaptdue to expansion under continuous maximum ed to receive three cables B side by side.

'20 load. V In Figures 5 and 6 the saddle A instead of Merely as a rough example a cable having being moulded integral with the conduit, is Y a copper 'core' of say .15 square inches in secformedwith a projection or key A which fits tion and with average insulation may be supinto a recess in the flanged end of one length ported in its duct by saddles approximately of the conduit and is kept in place by the ad- I 25 half-an-inch high and spaced two feet apart. jacent plain end of the next length.

The saddles may be moulded or otherwise' Figures 7 and 8 illustrate the invention as made inte ral with the conduit or duct and applied to a conduit divided longitudinally are shaped to suit the cross-sectional dimeninto two parts A and A 50 that the cable sions of the cable. When twooi' more cables may be laid rather than drawn in. In this 3 are laid side by side in the same conduit the construction the lower portion A of the conso saddles may he made with a corresponding duit is formed with recesses A into whichthe number of curved recesses. saddles A are inserted before the cable is In addition-to providing spaced supports laid and the cover A put on. Asshown in for the cable the saddles are advantageous in Figure 7 each length of the conduit may be as reducing friction when the cable is drawn in. formed with more than one of the recesses The sides of the saddles may be sloped or A so that the saddles, maybe spaced to suit curved so that they do not form abrupt ridges the part cular cable which is laid in the conor projections across the length of'the duct du1t. Figure 7 shows each length of conduit but rise gradually from the floor thereof. pzpvldedwlth onesaddle the other recess A 40 Thisfacilitates the drawing-in of the cable. mg left vacant. s

The main'p'ortion of the conduit or duct I n Figures 9 and lO-the conduit? is also may be of any usual form and material. It llvl I gI Hl Y but s D 17I' 1C- may, for instance, be in two parts one fitting tion the-lower portion A s formed with a or laid over the other.- In such-a case the number of'internally pro ecting teeth or 45 V saddles or raised portions according to this ridges and the saddle A? is provided with invention may he moulded or.' otherwise corresponding pro ections and recesses so formed integral with the lower portion. that one or more saddles may be placed n 'In the accompanying drawings, any desired positions in the conduit to suit Figures 1, 3, 5, 7 nd 9 are longitudinal the'requirements of the particular cable to be 50 sections through various constructions of laid therein. v v L In all the longitudinal sections the position of the cable when it sags due to expansion under continuous maximum load is indicated in chain lines.

The figures are to be regarded as diagram- 'matic and in practice the lengthof the con-' and the conduit in cases where the cable is drawn in. The function of the saddle is not in any way to insulate the conductor of the cable from the conduit for in a modern cable such insulation is adequately provided for in the construction of the cable itself.

What I claim as my invention and desire to secure by Letters Patent is 1. In an electric system embodying an insulated power cable adapted to carry a definite maximum load for an appreciable time interval, a conduit provided with raised saddles interiorly thereof at intervals in its length, said saddles being so proportioned and spaced in relation to the dimensions of the cable and the predetermined maximum load which it is intended to carry that the cable can sag freely, thus being free from compressive forces, until it has expanded to the extent brought about by continuous maximum load when it just rests upon the floor of the conduit.

2. In an electric system embodying an insulated power cable adapted to carr a definite maximum load for an apprecia letime interval, the combination with a conduit for encasing the cable and having the lower portion of the inner wall thereof formed with a plurality of recesses, of detachable saddles adapted to engage selected recesses and to form supports for the cable, the height of the saddles in relation to the dimensions of the cable and the predetermined maximum load which'it is intended to carry being such that the cable can sag freely, thus being free from compressive forces, until it has expanded to the extent brought about by continuous maximum load when it just rests upon the floor of the conduit.

8. In an electric system embodying an in- .sulated power cable adapted to carry a, definite maximum load'for an appreciable time interval, the combination with a conduit for encasing the cable, of supports for the cable within the conduit, said supports being so proportioned and spaced in relation to the dimensions of the cable and the predetermined maximum load Which it is intended to carry that the cable can sag freely, thus being free from compressive forces, until it has expanded to the extent brought about by continuous maximum load when it just rests 

